ABSTRACT/PROJECT SUMMARY The ability to rapidly modify gene expression in response to changes in specific environmental conditions is critically important to the survival and pathogenesis of disease causing bacteria, as these organisms encounter different environments throughout infection and transmission. It is well established that S. aureus experiences a subtle yet significant upshift in temperature as it transitions from sites of carriage such as the skin and anterior nares, to sites of infection such as blood and deep tissue. The ability to reliably sense and quickly modify gene expression in response to these changes in environmental temperature stands to facilitate the ability of S. aureus to survive within the human host and cause disease. RNA thermometers (RNATs) are cis-acting ribo-regulators that function to modulate translational efficiency in response to environmental temperature. RNATs are known to be important in controlling such key bacterial processes as nutrient acquisition, stress response and virulence. Despite the significance of S. aureus as a pathogen that must adapt to varied environmental temperatures, and the growing appreciation of RNATs as important temperature-responsive regulators of bacterial gene expression, the role of RNATs in controlling S. aureus gene expression has yet to be investigated. The aim of this exploratory study is to experimentally investigate the functionality of putative virulence-related RNATs identified by in silico analysis of the S. aureus USA300 genome. This goal will be achieved by the completion of the following step-wise experimental analyses: Step 1: Determine if select putative S. aureus RNATs are sufficient to confer temperature-dependent post-transcriptional regulation; Step 2: Investigate the role of the predicted inhibitory structure within each RNAT in mediating observed temperature-dependent post- transcriptional regulation; and Step 3: Validate targets that demonstrate temperature-dependent post- transcriptional regulation in S. aureus. The significance of these studies lies within the fact that they will advance the fundamental understanding of both RNATs, and the molecular mechanisms governing the production of S. aureus virulence factors. Advancing such knowledge is a necessary first step towards the production of novel therapeutics aimed at specifically disrupting S. aureus virulence gene expression, and by doing so, reducing or eliminating the ability of these significant pathogens to cause human disease. For this reason, the proposed studies are well aligned with the stated mission of the National Institutes of Health to ?foster fundamental creative discoveries, innovative research strategies, and their applications as a basis for ultimately protecting and improving health?.